BIOL 371 Lecture Notes - Lecture 6: Blastula, Body Cavity, Diploblasty
o Allows us to define other axes
▪ Anterior (front) vs posterior( back)
▪ Dorsal (back) vs ventral (front)
o Humans are triploblastic
Body cavities (coelom) of Bilateral
o Only in trophoblasts
o Cavity within the mesodermal tissue layer
▪ Outside of the gut
▪ Within the innermost layer
o Beause oelo is esoderal ad diplolasts do’t have esoderal layer
o Purpose
▪ Fluid transport within the organisms
▪ Provides a space to grow tissues at specific times of the year
• Example – gonads
▪ Makes a good hydrostatic skeleton
• To change the ody’s shape
▪ Good for absorbing shock
• Buffers internal organs from shock
▪ Does not apply to diploblasts
▪ Acoelomate
• No coelom
▪ Pseudocoelomate
• False coelom
• Not a cavity strictly within the mesodermal tissue layer
• Body cavity that is not completely lined by the mesoderm
• Body cavity is in contact with endoderm
▪ Coelomate/eucoelomate
• Fluid-filled cavity that is completely lined by the mesoderm
o Only comes into contact with mesoderm
• Even lined endoderm
• Body cavity that is completely lined by the mesoderm
o Body cavity is not in contact with the endoderm
o Developmental patterns
▪ Diploblasts
• Zygote
• 8-cell stage
• Blastula
• Gastrula
▪ Triploblasts
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